The present invention relates to arrangements for retaining an actuating member in an extreme position and for selectively releasing the actuating member.
An arrangement constructed in accordance with the present invention may be employed in hydraulic and pneumatic systems, wherever it is essential that the actuating member should be displaced at a high rate, e.g. in a valve in an emergency protection system, during fire-fighting, and during ejection from an aircraft, etc.
Furthermore, such arrangements may be used in emergency protection systems of electric power networks.
Already known are various arrangements for retaining an actuating member in an extreme position and for selectively releasing this member to perform a working stroke.
A known arrangement includes a housing receiving therein a pair of supports, one of the supports being secured in the housing and the other support being connected with a spring-biased connecting member held in permanent contact with the actuating member, e.g. with a valve of a hydraulic system. Wound between these two supports is at least one coil of wire selectively connectable to a power supply source.
The connecting link is in permanent contact with the actuating member to retain the latter in its extreme position, e.g. to retain a valve in a closed state. To release the actuating member, i.e. to open the valve, the wire coil is connected to the power supply source. As electric current then flows through the wire the latter heats up and expands as a result, whereby the support having the spring-biased connecting member attached thereto is displaced and moves the connecting member out of engagement with the acutating member, whereby the latter is released to perform a working stroke.
A disadvantage of the abovedescribed known arrangement is that the displacement of the connecting member cooperating with the actuating member is in direct proportion to the length of the wire coil, which leads to the necessity of increasing the dimensions of the arrangement, and, consequently, to its increased cost.